1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly, a reflective liquid crystal display device and a transflective liquid crystal display device.
2. Discussion of the Related Art
Until recently, display devices have typically used cathode-ray tubes (CRTs). Presently, many efforts and studies are being made to develop various types of flat panel displays, such as liquid crystal display (LCD) devices, plasma display panels (PDPs), field emission displays, and electro-luminescence displays (ELDs), as a substitute for CRTs. Of these flat panel displays, LCD devices have many advantages, such as high resolution, light weight, thin profile, compact size, and low voltage power supply requirements.
In general, an LCD device includes two substrates that are spaced apart and face each other with a liquid crystal material interposed between the two substrates. The two substrates include electrodes that face each other such that a voltage applied between the electrodes induces an electric field across the liquid crystal material. Alignment of the liquid crystal molecules in the liquid crystal material changes in accordance with the intensity of the induced electric field into the direction of the induced electric field, thereby changing the light transmissivity of the LCD device. Thus, the LCD device displays images by varying the intensity of the induced electric field.
FIG. 1 is a plan view illustrating a transflective LCD device according to the related art, and FIG. 2 is a cross-sectional view taken along a line II-II of FIG. 1.
Referring to FIGS. 1 and 2, the transflective LCD device 5 includes an array substrate, a color filter substrate, and a liquid crystal layer between the array substrate and the color filter substrate.
In the array substrate, a gate line 11 and a data line 30 cross each other to define a pixel region P on a first substrate 7. A thin film transistor Tr is formed at the crossing portion of the gate and data lines 11 and 30. The thin film transistor Tr includes a gate electrode 15, a semiconductor layer 20, and source and drain electrodes 32 and 34 spaced apart from each other. A gate insulating layer 17 is on the gate line 11 and the gate electrode 15.
A first passivation layer 38 is on the thin film transistor Tr and the data line 30 and has a first contact hole 40. A transmissive electrode 42 is on the passivation layer 38 in the pixel region P and contacts the drain electrode 34 through the first contact hole 40.
A second passivation layer 48 is on the transmissive electrode 42 and has a second contact hole 50 and a transmissive hole 51 in a transmissive region TA. A reflective electrode 52 is on the second passivation layer 48 in a reflective region RA. The reflective electrode 52 contacts the transmissive electrode 42 through the second contact hole 50.
In the color filter substrate, a black matrix 65 is formed on a second substrate 60 and corresponds to the gate and data lines 11 and 30 and the thin film transistor Tr. A color filter layer 69 including red (R), green (G) and blue (B) color filter patterns 69a, 69b and 69c is formed and corresponds to the pixel region P. A through hole 72 is formed in the respective color filter patterns 69a, 69b and 69c. A common electrode 75 is formed on the color filter layer 69.
As not shown in the drawings, first and second polarizing plates are formed on outer surfaces of the first and second substrates 7 and 60, respectively. A backlight unit is below the first substrate 7 and includes a reflective sheet, a plurality of lamps and a plurality of optical sheets to supply light.
In a reflective mode, the backlight unit is turned off and does not supply light, and an external light reflects on the reflective electrode 52 to display images. In a transmissive mode, the backlight unit is turned on and supplies light, and the light from the backlight unit passes through the transmissive hole 51 in the transmissive region TA to display images.
However, in the related art transflective LCD device, since the pixel region is divided into the reflective region and the transmissive region, when the LCD device is operated in both the reflective mode and the transmissive mode, about 50% of the area of the pixel region is used to display images. Accordingly, in both the reflective mode and the transmissive mode, actual aperture ratio and brightness is reduced, and thus, display quality is degraded.